This study uses a specialized laboratory configuration to examine how strongly convection can influence atmospheric radiation effects and to what extent greenhouse gases are causing warming or cooling under controlled conditions. A cylindrical apparatus is used, containing a heated, blackened aluminum plate that represents the Earth’s surface. This plate can be positioned either below or above the cooler cylinder wall, thereby enabling or suppressing convection. Adding controlled concentrations of the test gases HCG (hydrocarbon gas, a propane/isobutane mixture), CO₂, and argon, the interaction of radiation emitted by the plate with the gases and the resulting feedback to the plate is investigated. The results vary noticeably depending on the plate’s position and measurement duration. With the plate at the bottom, initially a strong temperature increase is observed. This is often falsely interpreted as greenhouse effect but is actually caused by temporarily suppressed convection due to the added gases. It is also demonstrated that the prerequisite for an atmospheric greenhouse effect – whether warming or cooling – is the presence of a tem- perature gradient along the radiation path. Although the experimental setup can only demonstrate part of the competing heat fluxes in the atmosphere, the results already show how these fluxes can relativize the influence of infrared-active gases.
